Slim profile indicating instruments

ABSTRACT

The present invention concerns the structure of and methods of constructing indicating instruments with slim profiles. The indicating instrument comprises a meter movement and a circuit board. The main body of the meter movement is situated in an aperture in the circuit board. With this placement, the front end of the body of the meter movement extends a distance in front of the circuit board and the back end of the meter movement body extends a distance behind the circuit board. Through appropriate selection and arrangement of any components on the circuit board, the circuit board can be constructed such that none of its components extend beyond the distance that the meter movement extends on either side of the circuit board. In this manner the space needed for the meter movement and the circuit board and its components collapses into the same area. A light plate may be added to the circuit board and meter movement. The light plate provides a structural framework for the indicating instrument. The circuit board and meter movement may be mounted to the light plate. In this manner, the internal components of the indicating instrument are all held together and can be calibrated and tested without the addition of any further components.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No.09/912,196 entitled “Slim Profile Indicating Instruments”, filed 23 Jul.2001, which claimed the benefit of U.S. provisional application No.60/220,456 entitled “Slim Profile Tachometer,” filed on 24 Jul. 2000.Each of the above-referenced applications is hereby incorporated byreference as though fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to an indicating instrument assembly ofany type and more directly to an assembly structure that decreases thedepth required for the instrument assembly.

[0004] 2. Description of the Related Art

[0005] Indicating instruments are used for numerous applications acrossa variety of industries and within innumerable types of machines,systems, and vehicles. Indicating instruments can, for example, measurethe speed of a vehicle, such as an automobile or airplane, or measurethe rotational speed of an engine shaft or turbine to indicate a need toswitch to an appropriate gear ratio so that the motor is not overworked.Indicating instruments can also be fuel, pressure, and temperaturegauges, which are found, for example, on vehicles, heavy equipment,assembly line apparatuses, and other industrial equipment. Complexvehicles and other equipment may have a variety of other special purposeindicating instruments to measure any recordable or gaugable activity orcondition. For example, airplanes and submarines may have altitude anddepth gauges, respectively.

[0006] In many situations it is desirable to construct an indicatinginstrument as small as possible because of size constraints of theenvironment in which it is used. For example, in an airplane cockpit alarge number of instruments must be placed in an extremely limited area.The size of the indicating instrument is considered not only as a factorof its exposed surface area as viewed by an operator, but also in termsof the amount of space taken, for example, under a mounting surface orbehind a panel, by the instrument's functional and mounting components.

[0007] In other instances, it is desirable that the exposed portion ofthe indicating instrument be quite large so that the operator can easilyperceive the presentation of the gauged information. In thesesituations, although it may be desirable to provide a large display forthe information, it may be equally desirable that the indicatinginstrument be otherwise small in size due to similar constraints ofspace for housing or mounting the underlying functional components. Anexample of these competing needs may be seen in the dashboardinstruments of an automobile such as speedometers and tachometers wherethe dial size is desired to be large for easy reading, but the mountingand housing space within the dashboard is limited.

[0008] Indicating instruments may also be manufactured for sale on the“aftermarket,” wherein additional instruments or devices, which wereunavailable as options on the vehicle or other equipment at the time oforiginal purchase, are provided for installation by the operator. In thecase of aftermarket indicating instruments such as speedometers ortachometers, these gauges may be provided for mounting on top of thedashboard or at another location in the vehicle for ease of viewing bythe operator. For example, many aftermarket tachometers are sold toautomobile operators involved in stock car racing. In such racing it isimportant for the operator to know when to shift, but it is imperativethat the operator be able to concentrate on the raceway and thecompetitor vehicles in order to avoid a collision. Many of these racingoperators prefer to mount an aftermarket tachometer on top of thedashboard, or otherwise in the area of the windshield, so they do nothave to lower their eyes from the road to read an original equipmenttachometer mounted within the dashboard.

[0009] Prior art indicating instruments 200, such as those shown inFIGS. 1A, 1B, 2A, and 2B, depict aftermarket tachometers with their ownhousings for dashboard mounting applications. Because of standard designconfigurations, these indicating instruments 200 are relatively deep inbody thickness from the face of the instrument to the back of thehousing. The thickness of these instruments 200 is dictated in largepart by the size of the meter movement 210, the rear end of which isgenerally mounted to a printed circuit board (PCB) 230. The metermovement 210 and PCB 230 assembly is then mounted to and within thehousing 240 of the indicating instrument 200, generally by mountingscrews 220 a and 220 b, to provide a firm support for the meter movement210, PCB 230, and related display components of the indicatinginstrument.

[0010] The indicating instrument of FIG. 2B is configured with dual PCBs230 and 230′, which further increases the necessary depth of the housingto enclose the additional PCB components. Generally a gap is also neededbetween the PCB 230′ and the rear of the housing 240 in order to allowroom for the circuit components mounted on and extending from the PCB230′, again deepening the housing. The design of mounting screws 220 aand 220 b, which extend beyond the housing in FIG. 2B, further increasethe overall depth of the indicating instrument.

[0011] In aftermarket applications, such significant depth of anindicating instrument can make it difficult to fit and install on thedashboard of a vehicle, especially in the case of a narrow dashboard ora steep windshield slope. In applications where the indicatinginstrument is integrated into the original design of the vehicle,machine, or other system control, the prior art designs of indicatinginstruments require relatively deep spaces to house their functionalcomponents.

SUMMARY OF THE INVENTION

[0012] The present invention concerns the structure of and methods ofconstructing indicating instruments with slim profiles. What is meant by“slim profile” is that indicating instruments according to thisinvention are of shallow depth or are relatively thin between the faceof the indicating instrument and the rear most component or the backpanel of any housing enclosing the indicating instrument.

[0013] At a base level, an indicating instrument according to thisinvention may comprise a meter movement and a circuit board. In order toachieve the slim profile, the main body of the meter movement issituated in an aperture in the circuit board. With this placement, thefront end of the body of the meter movement extends a distance in frontof the circuit board and the back end of the meter movement body extendsa distance behind the circuit board. Through appropriate selection andarrangement of any components on the circuit board, the circuit boardcan be constructed such that none of its components extend beyond thedistance that the meter movement extends on either side of the circuitboard. In this manner the space needed for the meter movement and thecircuit board and its components collapses into the same area.

[0014] In a further embodiment, a light plate may be added to thecircuit board and meter movement. The light plate may be seen as astructural framework for the indicating instrument. The light plate is arigid, refractive material, and in one embodiment is a molded plasticplate with boss mounts and boss extensions molded as protrusions fromthe back side of the light plate. The circuit board is mounted to theboss mounts extending from the light plate. In this way, the boss mountsprovide appropriate spacing between the light plate and the circuitboard to allow room for the front end of the main body of the metermovement and any components of the circuit board to reside. The metermovement may also be mounted to the back side of the light plate toprovide secure positioning of the meter movement relative to the rest ofthe components of the indicating instrument. In this manner, theinternal components of the indicating instrument are all held togetherand can be calibrated and tested without the addition of any furthercomponents. This provides a benefit in that significant disassembly isavoided in the event that a functional component is bad and needs to bereplaced.

[0015] In an alternative embodiment, the indicating instrument may havea second circuit board. This second circuit board may be positionedbetween the light plate and the first circuit board and similarlymounted to boss mounts extending from the light plate. In oneembodiment, the terminals of the meter movement may be directlyelectrically and mechanically attached to the second circuit board.

[0016] Aside from its structural function in this invention, the purposeof the light plate is to transmit light from a light source to the faceof an indicating instrument to illuminate the dial. In an embodiment ofthe present invention the light plate collects light from a lightsource, for example, a light bulb mounted on the circuit board, via aprojection from the back side of the light plate that contains anaperture. The aperture is large enough to surround the light bulbprojecting from the circuit board. In this manner, the light bulb needtake up no more space than the gap provided between the light plate andthe circuit board by the boss mounts and taken up by the meter movementand other circuit board components. The edges of the aperture in thelight plate surrounding the light bulb collect the emitted light andtransmit it through the light plate to its edge around the dial on theface of the indicating instrument where the light is emitted from thelight plate.

[0017] The indicating instrument may further have a pointer that travelsover the dial face. The pointer may be attached to a shaft extendingfrom the meter movement through apertures in the light plate and dialface. The pointer may move in a plane above and parallel to the dialface and underneath a lens. The pointer may be halted in its travel by apointer stop protruding from the dial face. In one embodiment, thepointer stop is a light emitting diode (LED) that further functions asan indicator of a condition of the indicating instrument. The LED iselectrically and mechanically connected to the circuit board andprotrudes through apertures in the light plate and dial face. Thepointer stop extends above the dial face far enough to intersect thesweep of the pointer and stop the movement of the pointer.

[0018] The various components of the indicating instrument may becontained in a housing for protection or for individually mounting theindicating instrument, for example, external to an instrument panelintegrated into the machinery for which the indicating instrument isproviding measurements. The housing may cover the back of the indicatinginstrument components and be fitted with a lens through which the faceof the indicating instrument may be viewed. In one embodiment, the lensis attached to the housing by a bezel surrounding circumferential edgesof the lens and housing, clamping the two together. A gasket may beplaced between the lens and both the housing and the edge of the lightplate as a cushion and a seal. Also, in one embodiment, the housing maybe formed with a circumferential ledge normal to the side wall. The bossextension of the light plate may extend beyond the edges of the circuitboard to make contact with the ledge. Due to the clamping pressure ofthe bezel transferred through the lens and the gasket to the light plat,the light plate, supported by the boss extension, is held firmly againstthe housing ledge.

[0019] In another embodiment of the invention, the lens of theindicating instrument is constructed with a concentric projection aroundthe edge of the face. This projection supports the bezel and preventsthe edge of the bezel from scratching or otherwise damaging, forexample, gouging or cracking, the optical surface of the lens. In yetanother embodiment of the indicating instrument, the concentricprojection of the lens may further be a channel bounded by two walls.Either the first wall or the second wall may provide the support to thebezel. In addition, the lens may have a concentric projection around theedge of the lens opposite the channel. With this lens construction, itis possible to place a lens on a relatively flat surface withoutscratching the optical surface of the lens. It is further possible tostack lenses on top of each other, for example, during shipping oflenses as individual components, with the projection of the second sidefitting into the channel of the first side. In this way, the opticalsurfaces of the lenses are separated from each other and the lenses areunable to rub against each other, thereby preventing scratching andother damage.

[0020] An indicating instrument with a housing may be mounted on varioussurfaces and in various configurations through the use of a mountingstrap that surrounds the housing. The mounting strap can be tightened orloosened around the housing through the use of a tightening means. Theindicating instrument may be rotated within the mounting strap andsecured at any position by tightening the tightening means. In oneembodiment, the tightening means may be a bolt with a nut that connectstwo ends of the mounting strap and draws them toward each other, therebytightening the mounting strap around the housing. Also attached to themounting strap may be a mounting foot, which can be attached to varioussurfaces at various angles. In one embodiment the mounting foot can besecured into a particular position by tightening the tightening means.In the particular embodiment wherein the tightening means is a bolt, themounting foot may similarly be held to the mounting strap by the boltand secured when the nut is tightened.

[0021] The indicating instrument may further have an external indicatorto indicate a condition of the indicating instrument. This may be thesame condition or a different condition than the condition indicated bythe pointer stop indicator in the embodiment previously described. Theexternal indicator may have a mounting foot that can be held between themounting strap and the housing of the indicating instrument, wherein themounting foot is attached to the indicating instrument. In anotherembodiment, the external indicator can be mounted at a location separatefrom the indicating instrument, but maintain communication with theindicating instrument, for example, by wires.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1A is a plan view of the face of a prior art indicatinginstrument.

[0023]FIG. 1B is a cross-sectional view of the prior art indicatinginstrument of FIG. 1A from the right side.

[0024]FIG. 2A is a plan view of the face of a second prior artindicating instrument.

[0025]FIG. 2B is a cross-sectional view of the prior art indicatinginstrument of FIG. 2B seen from the right side showing the use of twocircuit boards.

[0026]FIG. 3A is a plan view of the face of an embodiment of anindicating instrument according to the present invention.

[0027]FIG. 3B is a plan view of the right side of the indicatinginstrument of FIG. 3A.

[0028]FIG. 4A is a plan view of the face of an embodiment of anindicating instrument according to the present invention.

[0029]FIG. 4B is a cross-sectional view of the indicating instrument ofFIG. 4A taken along line 4B-4B.

[0030]FIG. 5 is an exploded isometric view of the construction of theface and circuit board assembly of an embodiment of an indicatinginstrument according to the present invention.

[0031]FIG. 6 is an exploded isometric view of the components of anembodiment of an indicating instrument according to the presentinvention.

[0032]FIG. 7A is a plan view of the front side of a circuit board of anembodiment of an indicating instrument according to the presentinvention.

[0033]FIG. 7B is a plan view of the back side of the circuit board ofFIG. 7A.

[0034]FIG. 8 is a cross-sectional view of an embodiment of an indicatinginstrument utilizing two circuit boards according to the presentinvention.

[0035]FIG. 9A is a plan view of the end of a switch shaft component usedwith an embodiment of an indicating instrument according to the presentinvention.

[0036]FIG. 9B is a first plan view of a portion of the surface along thelength of a switch shaft component used with an embodiment of anindicating instrument according to the present invention.

[0037]FIG. 9C is a second plan view of a portion of the surface of aswitch shaft component used with an embodiment of an indicatinginstrument according to the present invention.

[0038]FIG. 9D is a cross-sectional view of a knob for a switch shaftcomponent used with an embodiment of an indicating instrument accordingto the present invention.

[0039]FIG. 9E is a plan view of the bottom of the knob of FIG. 9D.

[0040]FIG. 9F is a fragmentary view, partially in cross-section, of anembodiment of an indicating instrument according the present inventiondetailing the placement of a switch.

[0041]FIG. 10A is a plan view of the front of a pointer used in anembodiment of an indicating instrument according to the presentinvention.

[0042]FIG. 10B is a partial cross-sectional view of the right side ofthe pointer of FIG. 10A.

[0043]FIG. 11 is a partial view in cross-section of stacked lenses usedin an embodiment of an indicating instrument according to the presentinvention.

[0044]FIG. 12 is a partial view in cross-section of the assembly of theface of an embodiment of an indicating instrument according to thepresent invention.

[0045]FIG. 13A is a plan view of a reflector, prior to assembly, for usein an external indicator of an embodiment of an indicating instrument ofthe present invention.

[0046]FIG. 13B is an isometric view of the reflector of FIG. 13Aassembled.

[0047]FIG. 14A is a cross-sectional view of a first configuration of astrap, strap pad, and housing in an embodiment of an indicatinginstrument according to the present invention.

[0048]FIG. 14B is a cross-sectional view of a second configuration of astrap, strap pad, and housing in an embodiment of an indicatinginstrument according to the present invention.

[0049]FIG. 15 is a plan view of the right side of an embodiment of anindicating instrument according to the present invention, wherein theexternal indicator is mounted on a surface apart from the body of theindicating instrument.

[0050]FIG. 16 is a plan view of the back of an embodiment of anindicating instrument according to the present invention with an accessplug removed.

[0051]FIG. 17 is a plan view of the back of the indicating instrument ofFIG. 16 with the access plug in place.

[0052]FIG. 18 is a plan view of the back of an embodiment of anindicating instrument according to the present invention with analternate wiring and access scheme.

[0053]FIG. 19 is a plan view of the right side of an embodiment of anindicating instrument according to the present invention with analternate configuration of the external indicator and the strap pad.

[0054]FIGS. 20A and 20B are plan views of the right side of anembodiment of an indicating instrument according to the presentinvention in alternate upside down mounting positions with the mountingfoot reversed.

[0055]FIGS. 20C and 20D are plan views of the right side of anembodiment of an indicating instrument according to the presentinvention in alternate upside down mounting positions with the mountingfoot facing forward.

[0056]FIGS. 20E, 20F, and 20G are plan views of the right side of anembodiment of an indicating instrument according to the presentinvention in alternate mounting positions with the mounting foot facingforward.

[0057]FIGS. 20H and 20I are plan views of the right side of anembodiment of an indicating instrument according to the presentinvention in alternate mounting positions with the mounting footreversed.

[0058]FIG. 20J is a plan view of the bottom of an embodiment of anindicating instrument according to the present invention, turned on itsright side.

DETAILED DESCRIPTION OF THE INVENTION

[0059] For the purposes of providing a detailed description of anindicating instrument according to the present invention, an aftermarketautomobile tachometer has been chosen as an exemplary embodiment fordescribing the novel features of the invention. The inventive design astranslated in the tachometer is merely one representation of theapplication of the novel construction techniques for indicatinginstruments disclosed herein, which are equally applicable to indicatinginstruments of all types. The tachometer is chosen because of the easeof describing the novel construction techniques as applied to thisparticular indicating instrument. In addition, an aftermarket embodimentis chosen as a means of detailing a complete set of features (forexample, an instrument including a housing), many of which would beinapplicable to an indicating instrument for an integrated application,such as if incorporated into an automobile dashboard display.

[0060]FIG. 3A shows the face 3 of an indicating instrument 1 (atachometer) of the novel configuration disclosed herein. Primaryelements of the indicating instrument seen in this view include: ahousing 2 (FIG. 3B); a bezel 4 that attaches a lens 6 to the housing 2;a gasket 8 to cushion the lens 6 and separate it from a light plate 10(FIG. 4B) and a dial face 14, which is seen through the lens 6 and isprinted with the instrument markings; and a pointer 16 with a pointercap 20, the pointer 16 indicating the instrument reading against themarkings on the dial face 14. For an aftermarket automotive application,the face 3 may be of a large diameter for ease of reading by the vehicleoperator. While the face 3 may be sizable, the depth of the indicatinginstrument 1, as viewed from the side in FIG. 3B, is substantially lessthan the typical prior art indicating instruments depicted in FIGS. 1Band 2B. The slim profile of the indicating instrument 1 is achievedthrough the novel component designs and mounting configurations of thepresent invention.

[0061]FIG. 4B depicts a cross-sectional view of the indicatinginstrument 1, wherein the cut-away of the section presented is indicatedby the broken line 4B-4B across the face 3 of the indicating instrument1 in FIG. 4A and the direction of the view is indicated by the arrows onthe ends of line 4B-4B. Other views that may aid the reader withreference to the following discussion may be found in FIGS. 5, 6, 7A,and 7B. As is readily seen, while the face 3 of the indicatinginstrument 1 is quite large for ease of viewing, the housing 2containing the components of the indicating instrument 1, in contrast,defines a very slim profile. A significant space savings is achievedthrough novel designs and arrangements of the components within thehousing of the indicating instrument 1.

[0062] The most significant space saving design feature is an aperturecreated in the printed circuit board (PCB) 70, the PCB hole 72, throughwhich the meter movement 52 is placed, rather than mounting the metermovement 52 behind the surface of the PCB 70 as in prior art designs.The meter movement 52 translates electrical impulses into rotationalmovement to move the pointer 16 around the dial face 14. By placing themeter movement 52 so that it extends through the plane of the PCB 70, aslimmer profile housing 2 can be used. The circuit components 134 (FIGS.7A and 7B) on each side of the PCB 70 may be chosen to extend no morethan the thickness of the meter movement 52 protruding from either sideof the PCB 70, thereby combining two depth intensive components in thesame space.

[0063] A second embodiment of an indicating instrument 1 according tothe present invention is shown in FIG. 8. In this instance, the diameterof the indicating instrument 1 is required to be smaller, for examplebecause of space constraints on the area allotted to the size of theface 3 in an instrument collection. It is often the case that a secondPCB 71 is then needed to accommodate all the circuit components that canno longer fit on a single, smaller-diameter PCB 70′. The concept ofproviding a hole in the PCB 70′ to encompass a component (e.g. the metermovement 52) can be expanded to the second PCB 71 to achieve a slimprofile indicating instrument 1, even with a decreased diameter. Themeter movement 52 may be mounted so that it extends through a hole inthe plane of the first PCB 70′ and the second PCB 71 may be mounted infront of meter movement 52, between the meter movement 52 and the lightplate 10.

[0064] The second PCB 71 may have multiple apertures for accommodatingvarious components in the indicating instrument 1. For example, in thesecond embodiment depicted in FIG. 8, the second PCB 71 has a lightplate hole 73 a for accepting the extension of the light plate 10 thatencircles the lamp 54 to collect the emitted light; a shaft hole 73 bthrough which the shaft 106 extending from the meter movement 52 extendsto connect with the pointer 16; one or more boss mount holes 73 callowing the boss mounts 12 to attach to the first PCB 70, and a potextension hold 73 d and a switch extension hole 73 e through which thepot shaft extension 24 and switch shaft extension 30, respectively, mayextend to protrude above the face 3 of the indicating instrument 1. Thesecond PCB 71 is held in radial alignment by the protrusion of thesevarious components through these various holes. The second PCB 71 isheld in axial alignment by the direct connection of the terminals 53 a,53 b (not shown in FIG. 8), and 53 c of the meter movement 52 to the PCB71. (In the embodiment of FIG. 7A, the terminals 53 a-c of the metermovement 52 are connected to the PCB 70 by meter movement leads 114a-c.) Through this novel configuration of the PCBs 70′, 71, the axiallength needed for the housing 2 covering the components of theindicating instrument 1 is minimized. In fact, the additional axiallength needed may be as little as the thickness of the second PCB 71.

[0065] As seen in prior art FIGS. 1B and 2B, the common internalmounting structure in the prior art indicating instruments 200 isthrough the use of long bolts 220 a-b and spacers 225 a-b that threadthrough the PCB 230 and the housing 240, thereby attaching thecomponents to the housing 240. The use of these bolts 220 a-badditionally increases the thickness of the prior art indicatinginstruments 200 because of the bolt heads and nuts needed to fasten thebolts 220 a-b in place.

[0066] A second, novel, space-saving technique of the present inventionis the use of a light plate 10 as the principle mounting structure inthe indicating instrument 1, as seen in FIG. 4B. Light transmissionbased on light pipe technology (the use of internally refractivecomposite materials that can reflect light to travel throughout thematerials' structure) is commonly used in indicating instrumentconstruction. Light pipes of various configurations are used in theprior art to transmit light from a light source to illuminate the faceof an indicating instrument. In an embodiment of the present invention,light pipe material is fabricated into a generally disk-shaped lightplate 10. The circumferential edges of the light plate 10 are beveled toreflect light, originating from behind the dial face 14, across the face3 of the indicating instrument 1. Lamp 54 interfaces with lamp socket56, which is mechanically and electrically connected with PCB 70 throughsocket aperture 108, thereby holding the lamp 54 in proper position andproviding electrical power to illuminate the lamp 54. The lamp 54 ispositioned within a aperture 110 protruding from the rear of the lightplate 10, whereby the edges of the light plate 10 surrounding theprotruding aperture 110 collect the emitted light from lamp 54 anddirect it to the face 3 of the indicating instrument 1.

[0067] In addition to transmitting light to the dial 14, this inventionfurther utilizes the light plate 10 as a mechanical framework to mountcomponents, align parts, and facilitate the manufacture and functioningof the indicating instrument 1. To achieve the benefits of a slimprofile for the indicating instrument 1, the light plate 10 may befabricated to include additional structures such as boss mounts 12 andboss extensions 32. The boss mounts 12 may be generally cylindricalappendages with either threaded molded holes or self tapping aperturesfor receiving mounting screws. The boss mounts 12 extend from the rearof the light plate 10 to create a gap between the light plate and PCB70. The PCB 70 is attached to the boss mounts 12 with mounting screws 62through mounting screw apertures 118 a-d (FIG. 6). The gap between thelight plate 10 and PCB 70 is sized to allow sufficient room for circuitcomponents 134 (FIGS. 7A and 7B) on the PCB 70, the extension of themeter movement 52 through the PCB 70, and other features to be describedherein.

[0068] The boss extensions 32 in the described embodiment may besmaller, shorter extensions from the light plate 10 that are sized tospace the light plate 10 away from a ledge 33 in the wall of the housing2. The boss extensions 32 provide firm axial alignment of the lightplate 10 against the housing 2 and thereby prevent axial movement of thePCB 70, of the meter movement 52, and of other components affixed to thelight plate 10 within the housing 2. The measurements of the boss mounts12, boss extensions 32, and housing ledge 33 are all chosen in relationto each other to provide appropriate spacing between components, whilestill achieving a slim profile for the indicating instrument 1.

[0069] The light plate 10 further supports and provides a mountingsurface for the dial face 14 and the meter movement 52. The dial face 14is situated directly upon a flat surface of the light plate 10. Metermovement mounts 112 a-b (FIG. 6) extend from the meter movement 52 andare attached to the light plate 10 with dial face screws 76 a-b. Thedial face screws 76 a-b also secure the dial face 14 to the light plate10 and further act to align the dial face with reference to the otherfunctional and display components on the face 3 of the indicatinginstrument 1. In this way, the light plate 10 acts as a framework tohold all functional parts as one assembly. This allows completecalibration and testing of the functional components of an indicatinginstrument 1 before installing the functional components in the housing2 or other environment and attaching any associated peripheral parts.The ability to test the functionality of an indicating instrument 1before it is encompassed in a housing 2 is a great benefit tomanufacturing economy, as malfunctioning components can easily bereplaced without having to take apart the entire indicating instrument1.

[0070] Another function of the light plate 10 is to provide radial andaxial alignment of the components with respect to the housing 2. Radialalignment is provided by the abutment of the exterior circumference ofthe light plate 10 with the internal wall 74 of the housing 2. In thisexemplary embodiment, PCB 70 also has alignment notches 137 a-b (FIG. 5)that mate with housing indentions 136 a-b (FIG. 6) in housing 2providing additional radial alignment and preventing rotational movementaround a center axis A. Since the PCB 70 is attached to the light plate10, the conjunction of the alignment notches 137 a-b and the housingindentions 136 a-b provide radial stability to all the components of theindicating instrument 1. Other means of radial alignment of componentsthrough an interface with the housing 2 are well known in the art. Axialalignment is provided by the contact between the boss extensions 32 andthe housing ledge 33 as described above. Axial alignment may also beaugmented by dimple 34 in the rear of the housing 2, which limits anymovement of the meter movement 52 in the housing 2.

[0071] The light plate 10 also receives holding pressure from the face 3of the indicating instrument 1, thereby further preventing axialrotation, by the combination of the lens 6 and a gasket 8. The gasket 8may be rubber, or other similar elastic but minimally compressivematerial, that provides spacing between the dial face 14 on the lightplate 10 and the lens 6 to allow room for the pointer 16 to sweep thedial face 14. The lens 6 is placed opposite the light plate 10,sandwiching the gasket 8 in between. The lens 6 is held against thegasket 8 by a bezel 4, which clamps around the circumference of the face3 of the indicating instrument 1, clasping the lens 6 along one edge ofthe bezel 4 and the housing 2 along a second edge of the bezel 4. Thecombination of the lens 6, gasket 8, light plate 10, bezel 4, andhousing 2 fixes the entire internal assembly of the indicatinginstrument 1 in place.

[0072] Additional projections from the light plate 10, extending in thedirection of the face 3 and identified as pot tube 66 and switch tube68, also prevent rotation of the various components relative to eachother. Pot tube 66 and switch tube 68 may be of unitary constructionwith the light plate 10 and extend though apertures in the dial face 14and lens 6, positively aligning the dial face 14 and the lens 6. The pottube 66 and switch tube 68 also provide good bearing surfaces for potshaft extension 24 and switch extension 30, which are further describedlater herein.

[0073] A design feature may be added to the pot tube 66 and switch tube68 to control unwanted light transmitted through the pot tube 66 andswitch tube 68 as they are integral to the light plate 10. This escapinglight is prevented by forming the ends of the pot tube 66 and switchtube 68 projections as conical surfaces 69 (of approximately 45°angles). See FIG. 9F. The conical surfaces refract the light harmlesslyinward toward the pot shaft extension 24 and the switch shaft extension30. Also, opaque tubing 64 a-b may be placed over the pot tube 66 andswitch tube 68 projections between the dial face 14 and the lens 6 tocontain unwanted light.

[0074] It is preferred that lens 6 have smooth polished surfaces withoptical clarity. However, this is not a requirement for thefunctionality of the invention. Prior art indicating instrument 200lenses 250, seen in FIGS. 1B and 2B are typically made as flat disks.The lens surfaces are very sensitive to scratching that can result iflenses are allowed to move and touch each other, which is usually thecase as prior art lenses are stacked for shipping or for availabilityduring the assembly of the indicating instruments 200. This can be avery serious problem, which often demands careful individual wrapping ofindividual lenses for storage and handling before assembly into theindicating instruments 200. The present invention solves the problem ofscratched lenses 6 by forming a concentric channel 5 and a concentricprojection 7 around the circumference of each lens 6, as shown to bestadvantage in FIG. 11. The concentric projection 7 of a first lens 6 canrest in the concentric channel 5 of a second lens 6, therebyinterlocking in such a way as to provide good separation and to preventradial movement between each lens 6 when stacked for shipping or use inassembly of indicating instruments 1. Thus the surfaces of lenses 6 arewell protected for bulk handling.

[0075] The lens 6 may also be protected from the sharp edge of the bezel4 upon assembly to prevent damage to the lens 6. Prior art indicatinginstruments 200, as seen in FIGS. 1B and 2B, typically add a spacer 260between the bezel 270 and lens 250. The present invention provides for aproper spacing between the sharp edge of the bezel 4 and the opticalsurface of the lens 6 as shown in FIG. 12. By spacing the walls formingthe concentric channel 5 to support the bezel 4 and designing theinterior wall forming the concentric channel 5 with a conical surface 9to mate with the angle of the bezel 4, the edge of the bezel 4 may bespaced apart from the surface of the lens 6. Designing the concentricchannel 5 to support the bezel 4 fulfills the need of protecting theoptics of the lens 6 without the cost of an extra part (i.e., a spacer)and its handling in production.

[0076] As shown, for example in FIGS. 4A and 4B, wherein the indicatinginstrument 1 is a tachometer, the lens 6 is constructed with twoapertures, a pot shaft aperture 25 and a switch shaft aperture 31,through which the pot tube 66 and switch tube 68 extending from thelight plate 10 pass, respectively. In the embodiment depicted, pot tube66 and switch tube 68 extend no further than the exterior surface of thelens 6. A pot shaft extension 24 and a switch shaft extension 30 extendfrom a pot 42 and a switch 36, respectively, mounted on the PCB 70,through the pot tube 66 and switch tube 68, respectively, and extendabove the exterior surface of the lens 6 for actuation by a user. Thisdesign eliminates the need for additional, bulky interface structures275 externally attached to the indicating instrument 200 for usercontrol, as seen in prior art FIGS. 1A and 2A. It may be desirable toprovide user accessible controls on the face 3 of other types ofindicating instruments 1, and the techniques and configurationsdescribed herein with reference to the example tachometer are not meantto be limited to only that embodiment, but may be used to provide othertypes of control mechanisms to various embodiments of indicatinginstruments 1.

[0077] In the case of an indicating instrument 1 that is a tachometer,as in this example embodiment, the pot 42 and switch 36 enable a user toset an RPM limit, at which point a shift indicator 26 is activated tosignal to a driver that the chosen RPM has been reached. When the switch36 is depressed, current from the pot 42 (e.g., a potentiometer) isallowed to pass to the meter movement 52 and sweep the pointer 16 to adesired RPM limit. By varying the pot, and the current through it, adesired RPM limit can be set. A clutch engagement 43, as seen in FIGS.4B and 5, is used between the pot shaft extension 24 and the pot 42 toprevent accidental re-setting of an indicator trigger point. Thisinvention incorporates a hard, smooth clutch ball 46 between a clutchspring 44 and a clutch base 48, all of which are contained in a cavityin the pot 42. The clutch base 48 interfaces with the pot shaftextension 24, but the clutch ball 46 and clutch spring 44 eliminatepossible torque transmittal to the pot 42 without depression of the potshaft extension 24, and thereby accidental resetting of the indicator 26limit, at very low cost. When the pot shaft extension 24 is depressedand rotated, the clutch base 48 pushes against the clutch ball 46 anddepresses the clutch spring 44, whereby a dog 50 on the pot shaftextension 24 engages a second dog 49 on the clutch base 48, therebytransmitting rotation from the pot shaft extension 24 to the pot 42 forsetting the RPM limit.

[0078] Attached to the external ends of the pot shaft extension 24 andthe switch shaft extension 30 are a pot knob 22 and a switch knob 28,respectively, for ease of grasp by a user, allowing a user to manipulateand control the pot 42 and switch 36 functions. Prior art typically usessetscrews or holding clips for knob to shaft attachment. The presentinvention uses a novel knob to shaft attachment system that is shown indetail in FIGS. 9A-F in exemplary fashion with respect to the switchknob 28 and switch shaft extension 30, but equally applicable to the potknob 22 and pot shaft extension 24, or any other knob to shaftattachments in any application.

[0079] The switch knob 28, which may be made of rubber or otherminimally compressive elastic material, has axial keys 125 moldedintegrally within a cavity 126 within the shift knob 28. The switchshaft extension 30 has mating axial keyways 124 molded in place. Theswitch shaft extension 30 also has a series of concentric barbs 122 thatallow easy installation of the switch knob 28 on the switch shaftextension 30. While the installation of the shift knob 28 on the switchshaft extension 30 is easy, the interference between the walls of theshift knob cavity 126 and the concentric barbs 122 on the switch shaftextension 30 prevent the easy removal of the shift knob 28. This knob toshaft system results in secure fixing of knobs on shafts at a lowmanufacturing cost.

[0080] Most indicating instruments with a sweeping pointer require apointer stop. Prior art pointer stops 280, as seen in prior art FIG. 2A,typically employ a small metal post riveted to the dial in the vicinityof the zero mark to ensure that pointer 285 is at the zero position whenthere is no power or no signal condition. An embodiment of the presentinvention, as shown, for example, in FIGS. 3A, 4A, and 4B, utilizes ashift indicator 26, which may be a light emitting diode, and whichconnects to the PCB 70, extending through an aperture 27 in the lightplate 10, and protruding through the dial face 14. The shift indicator26 may be placed in an appropriate location near the zero mark on thedial face 14 to act as a stop for the pointer 16. This eliminates thecost of a metal post and its assembly to the dial face 14, whileproviding a valuable signaling feature to the user.

[0081] In the depicted embodiments, the pointer 16 may be constructed ofmolded plastic. The pointer 16 is covered by a pointer cap 20, also ofmolded plastic, which has a shaft 21 (FIG. 4B) that extends through thepointer 16, the dial face 14, and the light plate 10 to engage the shaft106 extending from the meter movement 52. A detail of the pointerassembly is shown in FIGS. 10A and 10B. The pointer cap 20 also concealsthe pointer counterweight 18, which balances the pointer 16 as it movesthrough its sweep. A small hole 98 may be molded into the front of thepointer cap 20 and extend as a cavity through a length of the pointershaft 21. A rear cavity 99 in the opposite end of the pointer shaft 21also extends through a second length of the pointer shaft 21. In adeparture from the prior art, seen in FIG. 1A, in which the pointer 285is generally metallic with a through-hole for mounting the pointer 285on a shaft, the hole 98 in the pointer cap 20 and the rear cavity 99opposite it in the pointer shaft 21 are both blind holes in the presentinvention, but they come very close to meeting each other. A very thinmembrane 100 separates the pointer cap hole 98 from the rear cavity 99in the pointer shaft 21. As is known in the injection molding art,molding two blind holes is easier and less expensive than molding onethrough-hole.

[0082] Aside from being a subtle styling feature, the pointer cap hole98 has several useful purposes. First, the pointer cap hole 98 can beused with a special “pointer puller,” similar to a gear-puller, toremove the pointer 16 assembly from shaft 106 extending from the metermovement 52 during production if removal and replacement of pointer 16is needed. Use of a pointer-puller eliminates the possibility ofexcessive force being placed on the thrust bearing of the meter movement52 during removal of the pointer 16 from the shaft 106. From aninjection molding standpoint, the pointer cap hole 98 in the center ofthe pointer cap 20 reduces unsightly sink marks on the flat pointer cap20 surface that can result from the injection molding process.

[0083] In addition to the shift indicator 26 protruding from the face 3of the indicating instrument 1, it may be desirable to provide a userwith an external indicator to provide a greater degree of notificationof the conditions measured by the indicating instrument 1. In theexample embodiment of the tachometer described herein, an externalindicator 77, shown for example in FIGS. 4A and 4B, is provided as amore visible indicator of when the RPM threshold is reached. Theexternal indicator 77 may comprise a cylindrical housing 78, whichscrews into a threaded rear cap 80. The rear cap 80 may hold a lamp andsocket assembly 82, which illuminates the external indicator 77, therebyproviding the notification to the user. A lens 86 may be held in theindicator housing 78 by a retention ring 84, for example, a readilyavailable rubber O-ring. Such a retention ring 84 is easy to install,inexpensive, and the elasticity of the rubber compensates for tolerancevariations and provides rattle free operation.

[0084] A thin sheet of reflective material may be used for a reflector87 to improve the light output of external indicator 77. In oneembodiment, a die-cut piece of white or reflective material is rolledinto a conical shape and placed in the housing. See FIGS. 13A and 13B.The depicted embodiment includes special die cut ends for the reflector87, wherein the tabbed end 102 slips into the slotted end 104. Thedie-cut tabbed and slotted ends provide for easier handling of thereflector 87 during production and allow the reflector 87 to more easilystay in position. Once assembled, the conical form of the reflector 87is securely held together for easy installation.

[0085] As shown in FIGS. 4A, 4B, 15, and 19, the external indicator 77may be alternately mounted to the housing 2 or positioned apart from therest of the indicating instrument 1. In the depicted embodiments, theexternal indicator 77 is attached to a mounting bracket 88. In theembodiment shown in FIGS. 4, 4A and 4B, the mounting bracket 88 issecured between the rear cap 80 and the external indicator housing 78.The mounting bracket 88 is further secured to the housing 2 of theindicating instrument 1 by mounting strap 90. The bracket foot 89 of themounting bracket 88 is restrained under mounting strap 90 that issecured around the circumference of the housing 2. The bracket foot 89may be arced to fit against the curvature of the housing 2. FIG. 19depicts an embodiment wherein the bracket foot 89 is reversed in itsattachment to both the external indicator and the housing 2. In thisembodiment, the external indicator 77 is seated further back withrespect to the indicating instrument 1, which could be useful dependingupon the space configurations of the environment in which the indicatinginstrument 1 is to be mounted.

[0086] The embodiment of FIG. 15 shows the mounting bracket 88 mountedat a location remote from the indicating instrument 1. This embodimentallows the user to locate the external indicator 77 at a more optimallocation for conspicuous notice by a user. The bracket foot 89 canlikewise be reversed with respect to the external indicator 77 in thisembodiment. The bracket foot 89 of the mounting bracket 88 may have oneor more apertures 127 (FIG. 4B) to allow for a simple attachment of theexternal indicator 77 to a surface, such as by one or more screws 128(FIG. 15) placed through the apertures 127 and secured into the surface.

[0087] A means of communication is needed in order to mount the externalindicator 77 remotely from the indicating instrument 1. In theembodiment depicted in FIG. 15, this communication is accomplished bylead wires 58 a-b connected to lead connectors 116 a-b (FIGS. 7B and 16)on the PCB 70 at a first end and connected to the external indicator 77at a second end. The lead wires 58 a-b exit the rear of the housing 2via an aperture 59, as shown in FIGS. 16 and 17. The aperture 59 isdepicted in FIG. 17 with a plug 60 that itself has an aperture 61allowing the lead wires 58 a-b to pass through the plug 60 and connectto the external indicator 77. The plug may be rubber or similarminimally compressive, elastic material. The plug 60 protects the leadwires 58 a-b from potential damage by the potentially sharp edges of thehousing 2 forming the aperture 59, and also provides a removable seal toaccess components inside the housing 2.

[0088] The aperture 59 in the depicted embodiment is a large openingallowing the user to access several functional components of theindicating instrument 1. As discussed, the aperture 59 provides accessfor attachment of the lead wires 58 a-b to the lead connectors 116 a-bon the PCB 70. Aperture 59 further allows access to the lamp socket 56for removal and replacement of the lamp 54, for instance if the lamp 54burns out. Aperture 59 may also provide user access to controls forspecific configurations of the indicating instrument 1. In the exampleembodiment of the tachometer, the aperture 59 provides access to a dipswitch 120 for selection of the number of cylinders of the vehicle toprovide appropriate timing information to the tachometer so that it canaccurately measure the rotations of the engine.

[0089] In the embodiment depicted in FIGS. 16 and 17, the indicatinginstrument 1 further has a second aperture 39 in the rear wall of thehousing 2. This aperture 39 provides a passage for signal wires 38 a-dfrom their connection points on the PCB 70 to connection points in theenvironment from which they measure data. Signal wires 38 a-d may alsobe power transmission wires for providing power to the indicatinginstrument if needed. In the case of the tachometer example, two of thesignal wires, for example 38 a-b, are used to supply power to thetachometer. A third signal wire, for example 38 c, is used to measurespark firings through which the RPMs are measured. A fourth wire, forexample 38 d, is connected to the automobile's dash board illuminationswitch and supplies power for illumination of the indicating instrument.The aperture 39 is lined with a grommet 40 that itself has an aperture37 through which the signal wires 38 a-d pass. Similar to the plug 60,the grommet 40 protects the signal wires 38 a-d from the potentiallysharp edges of the housing 2 around the aperture 39. A conical surfaceas depicted (FIG. 4B) on the insertion edge of the depicted grommet 40enables easy installation of the grommet 40 within the aperture 39 byaxial pressure.

[0090] In another embodiment of an indicating instrument 1, as shown inFIG. 18, connections for lead wires 58 a-b and user setting interfacesmay be accessible at the surface of the housing 2 itself, withoutproviding access to the PCB 70. The indicating instrument 1 of FIG. 18is an embodiment wherein a selection switch 121 accessible through anaperture in the housing 2 allows the user to make a cylinder numberselection for the vehicle. Similarly, a protruding clip connector 117provides an easily accessible attachment means for the lead wires 58a-b. Access to other user options and functionality connections for anindicating instrument 1 may similarly be provided.

[0091] The mounting strap 90 described previously and shown in FIGS. 4B,14A, 14B, 15, 18, and 19 may be a metal band formed to fit around thecircumference of the housing 2. The mounting strap 90 may have outturnedends 91 a-b that are held together around the housing 2 by a mountingbolt 95 and nut 96. A constant distance may be maintained betweenoutturned ends 91 a-b by a bolt sleeve 97 placed around the shaft of themounting bolt 95 between the outturned ends 91 a-b. Any otherconventional means for tightening or clamping the mounting strap 90around the housing 2, for example, a clamp, a buckle, and a compressivespring force inherent in the mounting strap 90, are contemplated withinthe scope of the invention. A strap pad 92, for example of rubber orsimilar minimally compressive, elastic material, designed to wrap aroundmetal strap 90 may additionally be placed on the mounting strap 90. Thewrap-around design of the strap pad 92 covers the potentially sharpedges of the mounting strap 90 providing better safety and appearance.Small ribs 133 may be formed on the bottom side of the strap pad 92, asshown in FIGS. 4B and 14B, to provide, for example, extra flexibilityfor good conformance of the mounting strap 90 to irregularities in thehousing 2 surface, a high friction interface between the housing 2 andmounting strap 90 preventing movement therebetween, and accommodationfor the extra thickness of the bracket foot 89 of the external indicator77 mounting bracket 88. The strap pad 92 may be optionally mounted onmounting strap 90 with the ribs 133 facing radially outwards as shownin, for example, FIGS. 14A and 19 for a different aesthetic appearance.

[0092] Once assembled, the mounting strap 90, strap pad 92, and mountingbolt 95 assembly holds itself together around the housing 2. Theassembly also allows for easy adjustment of radial position of theindicating instrument 1 within the mounting strap 90 by simply looseningthe mounting bolt 95 and rotating the indicating instrument 1. Thedesign allows the indicating instrument 1 to be rotated 360° in relationto mounting strap 90 and mounting foot 94. This provides maximumflexibility and adaptability for installation of indicating instrument1.

[0093] The mounting foot 94 may be similarly attached to the mountingstrap 90 by the mounting bolt 95, and thereby pivot around the axis ofthe mounting bolt 90. The design of the mounting foot 94 offers greatflexibility of positioning and use of the indicating instrument 1 asshown in FIGS. 20A-J. The mounting foot 94 may be attached to pointforward, as in FIGS. 20C-G and 20J, or to the rear, as in FIGS. 20A-Band 20H-I, allowing the indicating instrument 1 varying degrees of tiltin the mounted placement. Any particular angular position of theindicating instrument 1 with respect to the mounting foot 94 may be heldby simply tightening the mounting bolt 95 and nut 96. The mounting footmay similarly be rotated 360° with respect to the indicating instrumenthousing 2 by rotating the mounting strap 90 around the housing 2. Suchversatility in the mounting foot 94 allows the indicating instrument 1to be mounted in diverse positions and locations and be placed into manydifferent environments. For example, with a tachometer embodiment, byrotating the mounting foot 94 around the mounting bolt 95 and rotatingthe mounting foot 94 around the housing 2, the tachometer couldvariously be mounted in an automobile, for example, to the dashboard,the underside of the roof, a window column, a reinforcement post, or aroll bar.

[0094] Attachment of the mounting foot 94 to various surfaces may beachieved in a number of ways. The mounting foot may be provided withapertures 132 a-b in its base for the reception of in attachment means,for example screws. Mounting foot 94 may further be configured with anarch 93 in its base so that the mounting foot 94 may better conform to acurved surface such as a window column, reinforcement post, or roll bar.The mounting foot 94 may further be provided slots 130 for theacceptance of a band for retaining the indicating instrument 1 against asurface. The band may be for example, a fabric or plastic strap, or evenan hose clamp, that may slip thorough the slots 130 and around amounting surface such as a reinforcement post or roll bar. The mountingfoot 94 may further be attached to a surface with an adhesive placedbetween the mounting foot 94 and the surface.

[0095] Although various embodiments of this invention have beendescribed above with a certain degree of particularity, or withreference to one or more individual embodiments, those skilled in theart could make numerous alterations to the disclosed embodiments withoutdeparting from the spirit or scope of this invention. It is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative only ofparticular embodiments and not limiting. Changes in detail or structuremay be made without departing from the basic elements of the inventionas defined in the following claims.

What is claimed is:
 1. A lens comprising: a first face; the first face comprising a concentric channel around a circumferential edge of the lens; and a second face; the second face comprising a concentric projection around the circumferential edge of the lens; wherein when at least two lenses are stacked upon each other, the concentric projection of the second face of a first lens engages the concentric channel of the first face of a second lens, preventing relative movement between the first lens and the second lens; and maintaining a gap between the second face of the first lens and the first face of the second lens.
 2. A lens as described in claim 1, wherein at least a portion of the first face comprises an optical surface; and the concentric channel further comprises: a first wall; and a second wall; wherein the first wall and the second wall form the bounds of the concentric channel; and at least one of the first wall and the second wall projects above the optical surface; wherein the optical surface of the first face is protected from scratches and other damage when the lens is set upon a generally flat surface.
 3. A lens as described in claim 1, wherein at least a portion of the second face comprises an optical surface; and the concentric projection projects above the optical surface; wherein the optical surface of the second face is protected from scratches and other damage when the lens is set upon a generally flat surface.
 4. A knob assembly comprising: a knob; the knob containing a generally cylindrical cavity formed by a contiguous interior wall of the knob; the interior wall further comprising at least one key protruding into the cavity; and a shaft with a generally cylindrical first end, the first end of the shaft further comprising: at least one concentric barb formed around the first end of the shaft, wherein the circumference of the barb is slightly larger than the circumference of the cavity; and at least one keyway formed to accept the key in the knob cavity, the keyway interrupting the contiguity of the at least one concentric barb; wherein when the key in the cavity and keyway on the shaft are aligned, the knob may be pushed upon the first end of the shaft, the first end of the shaft thereby filling the cavity, and the interface of the at least one barb with the interior wall of the knob inhibiting the knob from being pulled off the shaft, and the interface of the at least one key and the at least one keyway preventing the knob from rotating relative to the shaft.
 5. A knob assembly as described in claim 4, wherein the knob is constructed of a minimally compressive, elastomeric material.
 6. A knob assembly as described in claim 5, wherein the elastomeric material comprises rubber. 